Section 2 (2-2) Measuring Earthquakes

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Vocabulary

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P waves- earthquake waves that compress or expand the ground like an accordion.
S waves- earthquake waves that is the kind of seismic waves and vibrate from side to side and also up and down.
seismograph- a machine that records the ground movements caused by seismic waves and movement on the fault.
focus- the place under the Earth's surface where rocks under stress breaks causing an earthquake.
epicenter- the place in the surface right under the focus.
seismic waves- it carries energy of earthquake and it vibrates.
surface waves- a kind of seismic waves that are slower than P and S waves, but surface waves cause more ground movements.
magnitude- a measurement of earthquake strength based on seismic waves and movements along faults.
Mercalli scale- rates earthquakes according to their intensity.
Richter scale- a rating of the size of seismic waves as measured by a specific type of mechanical seismograph.
Moment Magnitude scale- a rating system that estimates the total amount of energy released by an earthquake

Outline

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Seismic Waves

• as seismic waves travel through the earth, they carry the energy of earthquakes
  • seismic waves carry this energy from the focus to the surface

Earth

• earthquakes release 2 types of seismic waves
  • P waves and S waves
    • they travel in all directions and cause vibrations
• after they reach the surface they become surface waves

Earthquake Scales

• there is three scales used to measure earthquakes
  • the Moment Magnitude scale
    • used to determine magnitude of an earthquake
• other scales
  • Mercalli scale
  • Richter scale

Diagram of the epicenter

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